Ab-initio study of Nb-based complex materials: A new class of materials for optoelectronic applications

We have studied electronic, optical and spintronic properties of Nb based complex materials NaNdANbO(6)F (A= Ti, Zr, Co, Ni) by using density functional theory (DFT) calculations. State-of-the-art generalized gradient approximation is used by adding Hubbard correction (GGA+U) to treat exchange-correlation potential of the electronic system. From the energy band structures, we observed that NaNdTiNbO6F (3.7 eV) and NaNdZrNbO6F (4.0 eV) are direct and indirect band gap materials, respectively. However, NaNdCoNbO6F and NaNdNiNbO6F are halfmetallic compounds having energy band gaps in spin (up arrow) (spin (down arrow)) channel of 2.2 (1.75) and 2.5 (3.6) eV, respectively. Effective contributions of different compounds and electronic states are analyzed by studying total and partial density of states. These compounds are potential candidates to be utilized in spintronic devices as they have significant values of magnetic moments, shown in Table 1. We have used an energy range of 0-14 eV to calculate and explain important optical characteristics of NaNdANbO(6)F (A= Ti, Zr, Co, Ni). These material falls in the category of optically active materials as their values of n(omega) lie between 1.0 and 2.0. These compounds are also potential candidates for the anti-reflective coating applications as they reflect maximum of 45 % of incident photons in upper UV region. Finally, optical parameters are also used to explain contributions of inter-band electronic transitions in these compounds. This study might be considered as first quantitative theoretical study of magnetic, electronic and optical behavior in the tetragonal phases of these Nb based complex materials.